I would not use a static converter on a difficult load, and you may get some surface finish issues (this has been reported with surface grinders using static converters). If you want the simple approach, probably an RPC. Since it is a bit more difficult load I would recommend a 7.5 Hp. A Y connection motor that does not connect to neutral would not need a transformer, it is what the motor sees for each phase as long as it is floating relative to neutral/ground. You can speak to the RPC manufactures and they can give you more details and recommendations. If you need 120 VAC, you would just use either L1 or L2 and neutral, not the manufactured leg. Also as I outlined previously, the transformer needs to be run off of L1 and L2, not the manufactured leg. You can purchase an RPC panel for under $200 if you can find a decent motor locally.
A VFD will be close to the cost of the RPC, and then you need an enclosure, power switch, fusing and rewire your lathe/control system. It all adds up, and if you just want phase conversion then an RPC is more cost effective. I have seem the American Rotary AMP cubes, they are very nice but more expensive. American rotary gives discounts, so if you watch certain Youtube videos they will have a discount code also Bar Z Bash 2019 there was a discount code. Others may have more info.
